In recent years, a photocatalyst such as titanium oxide has been used in many applications including an exterior material of an architectural structure. By utilizing an activity of the photocatalyst excited by a light energy, various harmful substances can be decomposed, or by hydrophilizing a film surface coated with a photocatalyst, a dirt which is attached to the film surface can be readily washed out with water. Followings are known as technologies to obtain a photocatalyst coated body coated with the photocatalyst mentioned above.
With regard to a composition to form a photocatalyst coated film on a surface of a substrate, for example, as described in WO 1995/11751 (Patent Literature 1), a mixture composition of a photocatalyst particle with a binder including a precursor to a silicone resin film, a silica fine particle, an alumina fine particle, and a mixture thereof is known.
Further, in a case that a hydrophilic photocatalyst coated film is formed on an organic substrate, as described in WO 1999/63011 (Patent Literature 2), in order to obtain a transparent and uniform photocatalyst coated film and to suppress deterioration of the painted surface due to photooxidation, a technology is shown wherein an intermediate layer is formed with a surface treating agent including a nonionic surfactant, or a fluorine based surfactant, or a mixture of them; a water-soluble solvent having a boiling point of 180 to 235° C., or an alcohol having 1 to 4 carbon atoms, or water, or a mixture of two or more of them; and a colloidal silica.